As lithography still pushing toward to low-k1 region, resolution enhancement techniques (RETs) including source
optimization (SO) and mask optimization (MO) are expected to overcome the fundamentally physics in optics. Recently
inverse lithography (IL) is widely studied for source and mask optimization (SMO) to enhance the resolution for over
diffraction limit integrate circuit (IC) patterns. In this paper, we propose a gradient based SMO algorithm where the SO
and MO are two sequential steps due to their different image formation mechanism. Moreover, we employ three cost
functions including aerial and resist image and the image contrast which is proposed in our previous work. We show that
IL patterns produced by SMO have better pattern fidelity and image contrast than MO only patterns.